Fix Text incorrect line height

Summary:
Setting the line height with the help of Android-provided StaticLayout is incorrect. A
simple example app will display the following when `setLineSpacing(50.f, 0.f)`
is set: {F62987699}. You'll notice that the height of the first line is a few
pixels shorter than the other lines.
So we use a custom LineHeightSpan instead, which needs to be applied to the text
itself, and no height-related attributes need to be set on the TextView itself.

Reviewed By: lexs

Differential Revision: D3841658

fbshipit-source-id: 7257df4f1b2ce037554c7a7a5ca8f547a2056939

ReactAndroid/src/main/java/com/facebook/react/views/text/CustomLineHeightSpan.java

@@ -0,0 +1,54 @@
+// Copyright 2004-present Facebook. All Rights Reserved.
+
+package com.facebook.react.views.text;
+
+import android.graphics.Paint;
+import android.text.style.LineHeightSpan;
+
+/**
+ * We use a custom {@link LineHeightSpan}, because `lineSpacingExtra` is broken. Details here:
+ * https://github.com/facebook/react-native/issues/7546
+ */
+public class CustomLineHeightSpan implements LineHeightSpan {
+  private final int mHeight;
+
+  CustomLineHeightSpan(float height) {
+    this.mHeight = (int) Math.ceil(height);
+  }
+
+  @Override
+  public void chooseHeight(
+      CharSequence text,
+      int start,
+      int end,
+      int spanstartv,
+      int v,
+      Paint.FontMetricsInt fm) {
+    // This is more complicated that I wanted it to be. You can find a good explanation of what the
+    // FontMetrics mean here: http://stackoverflow.com/questions/27631736.
+    // The general solution is that if there's not enough height to show the full line height, we
+    // will prioritize in this order: ascent, descent, bottom, top
+
+    if (-fm.ascent > mHeight) {
+      // Show as much ascent as possible
+      fm.top = fm.ascent = -mHeight;
+      fm.bottom = fm.descent = 0;
+    } else if (-fm.ascent + fm.descent > mHeight) {
+      // Show all ascent, and as much descent as possible
+      fm.top = fm.ascent;
+      fm.bottom = fm.descent = mHeight + fm.ascent;
+    } else if (-fm.ascent + fm.bottom > mHeight) {
+      // Show all ascent, descent, as much bottom as possible
+      fm.top = fm.ascent;
+      fm.bottom = fm.ascent + mHeight;
+    } else if (-fm.top + fm.bottom > mHeight) {
+      // Show all ascent, descent, bottom, as much top as possible
+      fm.top = fm.bottom - mHeight;
+    } else {
+      // Show proportionally additional ascent and top
+      final int additional = mHeight - (-fm.top + fm.bottom);
+      fm.top -= additional;
+      fm.ascent -= additional;
+    }
+  }
+}

ReactAndroid/src/main/java/com/facebook/react/views/text/ReactTextShadowNode.java

@@ -172,6 +172,12 @@ public class ReactTextShadowNode extends LayoutShadowNode {
                     textCSSNode.mTextShadowRadius,
                     textCSSNode.mTextShadowColor)));
       }
+      if (!Float.isNaN(textCSSNode.getEffectiveLineHeight())) {
+        ops.add(new SetSpanOperation(
+                start,
+                end,
+                new CustomLineHeightSpan(textCSSNode.getEffectiveLineHeight())));
+      }
       ops.add(new SetSpanOperation(start, end, new ReactTagSpan(textCSSNode.getReactTag())));
     }
   }
@@ -235,14 +241,6 @@ public class ReactTextShadowNode extends LayoutShadowNode {
           // technically, width should never be negative, but there is currently a bug in
           boolean unconstrainedWidth = widthMode == CSSMeasureMode.UNDEFINED || width < 0;
 
-          float effectiveLineHeight = reactCSSNode.getEffectiveLineHeight();
-          float lineSpacingExtra = 0;
-          float lineSpacingMultiplier = 1;
-          if (!Float.isNaN(effectiveLineHeight)) {
-            lineSpacingExtra = effectiveLineHeight;
-            lineSpacingMultiplier = 0;
-          }
-
           if (boring == null &&
               (unconstrainedWidth ||
                   (!CSSConstants.isUndefined(desiredWidth) && desiredWidth <= width))) {
@@ -253,8 +251,8 @@ public class ReactTextShadowNode extends LayoutShadowNode {
                 textPaint,
                 (int) Math.ceil(desiredWidth),
                 Layout.Alignment.ALIGN_NORMAL,
-                lineSpacingMultiplier,
+                1.f,
-                lineSpacingExtra,
+                0.f,
                 true);
           } else if (boring != null && (unconstrainedWidth || boring.width <= width)) {
             // Is used for single-line, boring text when the width is either unknown or bigger
@@ -264,8 +262,8 @@ public class ReactTextShadowNode extends LayoutShadowNode {
                 textPaint,
                 boring.width,
                 Layout.Alignment.ALIGN_NORMAL,
-                lineSpacingMultiplier,
+                1.f,
-                lineSpacingExtra,
+                0.f,
                 boring,
                 true);
           } else {
@@ -275,8 +273,8 @@ public class ReactTextShadowNode extends LayoutShadowNode {
                 textPaint,
                 (int) width,
                 Layout.Alignment.ALIGN_NORMAL,
-                lineSpacingMultiplier,
+                1.f,
-                lineSpacingExtra,
+                0.f,
                 true);
           }
 
@@ -588,7 +586,6 @@ public class ReactTextShadowNode extends LayoutShadowNode {
           UNSET,
           mContainsImages,
           getPadding(),
-          getEffectiveLineHeight(),
           getTextAlign()
         );
       uiViewOperationQueue.enqueueUpdateExtraData(getReactTag(), reactTextUpdate);

ReactAndroid/src/main/java/com/facebook/react/views/text/ReactTextUpdate.java

@@ -10,7 +10,6 @@
 package com.facebook.react.views.text;
 
 import android.text.Spannable;
-import android.view.Gravity;
 
 import com.facebook.csslayout.Spacing;
 
@@ -28,7 +27,6 @@ public class ReactTextUpdate {
   private final float mPaddingTop;
   private final float mPaddingRight;
   private final float mPaddingBottom;
-  private final float mLineHeight;
   private final int mTextAlign;
 
   public ReactTextUpdate(
@@ -36,7 +34,6 @@ public class ReactTextUpdate {
     int jsEventCounter,
     boolean containsImages,
     Spacing padding,
-    float lineHeight,
     int textAlign) {
     mText = text;
     mJsEventCounter = jsEventCounter;
@@ -45,7 +42,6 @@ public class ReactTextUpdate {
     mPaddingTop = padding.get(Spacing.TOP);
     mPaddingRight = padding.get(Spacing.END);
     mPaddingBottom = padding.get(Spacing.BOTTOM);
-    mLineHeight = lineHeight;
     mTextAlign = textAlign;
   }
 
@@ -77,10 +73,6 @@ public class ReactTextUpdate {
     return mPaddingBottom;
   }
 
-  public float getLineHeight() {
-    return mLineHeight;
-  }
-
   public int getTextAlign() {
     return mTextAlign;
   }

ReactAndroid/src/main/java/com/facebook/react/views/text/ReactTextView.java

@@ -20,7 +20,6 @@ import android.view.Gravity;
 import android.view.ViewGroup;
 import android.widget.TextView;
 
-import com.facebook.csslayout.FloatUtil;
 import com.facebook.react.uimanager.ReactCompoundView;
 import com.facebook.react.uimanager.ViewDefaults;
 import com.facebook.react.views.view.ReactViewBackgroundDrawable;
@@ -65,16 +64,6 @@ public class ReactTextView extends TextView implements ReactCompoundView {
       (int) Math.ceil(update.getPaddingRight()),
       (int) Math.ceil(update.getPaddingBottom()));
 
-    float nextLineHeight = update.getLineHeight();
-    if (!FloatUtil.floatsEqual(mLineHeight, nextLineHeight)) {
-      mLineHeight = nextLineHeight;
-      if (Float.isNaN(mLineHeight)) { // NaN will be used if property gets reset
-        setLineSpacing(0, 1);
-      } else {
-        setLineSpacing(mLineHeight, 0);
-      }
-    }
-
     int nextTextAlign = update.getTextAlign();
     if (mTextAlign != nextTextAlign) {
       mTextAlign = nextTextAlign;

ReactAndroid/src/main/java/com/facebook/react/views/textinput/ReactTextInputShadowNode.java

@@ -129,7 +129,6 @@ public class ReactTextInputShadowNode extends ReactTextShadowNode implements
           mJsEventCount,
           mContainsImages,
           getPadding(),
-          getEffectiveLineHeight(),
           mTextAlign
         );
       uiViewOperationQueue.enqueueUpdateExtraData(getReactTag(), reactTextUpdate);